Along with the developments in large-capacity recording media and broadband networks, a content distribution system via a recording medium has been prevalent, where a digital content (hereinafter, simply “content”), such as a digitized movie work or a digitized music work, is recorded on a recording medium and distributed.
In such a system, it is necessary that a content is played back or copied only under restrictions imposed by an agreement between the copyright holder and the user of the content, in order to protect the copyright of the content.
As a conventional technique for protecting digital works from unauthorized copying and the like, a method using encryption is well-known. Meanwhile, due to a rapid increase in the use of mobile phones and smart phones, there is a growing demand from users to enjoy browsing contents with such mobile phones.